Recently, a portable terminal having a front side and a back side on which cameras are built is on the market. As a technology of transmitting data between portable terminals is rapidly changing, videotelephony through which users speak to each other while seeing their faces using cameras built in the portable terminals is becoming more common.
The videotelephony has an advantage of giving familiarity since it is possible to see an opposite party, but it is vulnerable to the security since all images recognized by a camera are exposed to the opposite party. In particular, in an area, such as military facilities or industrial facilities, where the security is required, important information may be leaked through the videotelephony. In addition, in case that another person who is not a person talking on a videophone sees the opposite party during the videotelephony, personal information of the opposite party may be exposed.